Progress in neurological surgery
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The field of peripheral nerve stimulation (PNS) is now experiencing a phase of rapid growth in number of patients, number of implanters, number of indications, and procedure types. This, however, appears to be only a beginning of major developments that could revolutionize the field of PNS. It is expected that the progress in PNS will continue simultaneously in several directions as new indications, new stimulation targets and new device designs evolve in the foreseeable future. ⋯ Expanding the number of applications will without question strengthen the field of PNS. The turning point, however, will not occur until sufficient scientific evidence is gathered to unequivocally prove its safety, clinical efficacy and cost-effectiveness, and when PNS applications become officially endorsed through regulatory approval of each indication. Such changes will allow implanters to use approved devices for approved indications--instead of the contemporary 'off-label' use--and at the same time give device manufacturers a chance to market these devices and support education on their appropriate use.
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Since its inception in the 1970s, peripheral neuromodulation has become an increasingly common procedure to treat chronic neuropathic disorders. Historically, peripheral nerve stimulation (PNS) originated with the placement of large surface cuff electrodes, which was refined by the introduction of functional nerve mapping with circumferential electrical stimulation. This substantially improved the targeting of sensory fascicles. ⋯ To further refine functional mapping for the placement of these percutaneous electrodes, radiofrequency needle probes have more recently been employed to elicit paresthesias in awake patients to map the pain generators and guide treatment. In this chapter, we provide a description of the development and basic mechanisms of peripheral nerve stimulation, as well as a more detailed description of the two most commonly employed forms of peripheral nerve stimulation: occipital nerve stimulation for occipital neuralgia, and subcutaneous peripheral nerve field stimulation to stimulate free nerve endings within the subcutaneous tissue when the pain is limited to a small, well-localized area. The closely related ideas of internal and external targeted subcutaneous stimulation are also discussed.
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Subcutaneous occipital nerve region stimulation is becoming an important part of the overall treatment regimen for a number of chronic headache syndromes refractory to nonsurgical, medical management. A combination of improved device technology and methodology, further understanding about appropriate indications and achievement of on-label FDA status should support continued use and success of this neuromodulation modality.
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The effect of peripheral neurostimulation has traditionally been attributed to the activation of non-noxious afferent nerve fibers (Aβ-fibers) thought to modulate Aδ and C-fiber-mediated nociceptive transmission in the spinal cord, compatible with the 'gate control theory of pain'. The concept has been extended since its initial description and more recent experimental evidence suggests that the analgesic effects of peripheral nerve stimulation in pain states such as in chronic headache require an interplay of multiple influences. ⋯ Beyond the concept of neuromodulation--decreasing excitation or increasing inhibition--a prerequisite of this arrangement is the convergence of different types of afferent activity and an intact descending modulatory network. In this review, we focus on the functional anatomy, pathophysiological mechanisms and neurophysiological and pharmacological findings elucidating the central mechanisms of peripheral nerve stimulation.
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Spinal nerve root stimulation (SNRS) is a neuromodulation technique that is used to treat chronic pain. This modality places stimulator electrode array(s) along the spinal nerve roots, creating stimulation paresthesias within the distribution of the target nerve root(s), thereby treating pain in that same distribution. ⋯ SNRS combines the minimally invasive nature, central location, and ease of placement of spinal cord stimulation with the focal targeting of stimulation paresthesias of peripheral nerve stimulation. This hybrid technique may be an effective alternative for patients in whom other forms of neurostimulation are either ineffective or inappropriate.